1. Field of Invention
The present invention relates to a Direct Broadcast Satellite (DBS) system. More particularly, the invention relates to a method and apparatus for selecting one of a plurality of information signals broadcast from at least one satellite in the Direct Broadcast Satellite (DBS) system.
2. Description of the Background Art
Direct Broadcast Satellite (DBS) content providers have chosen to use multiple satellite networks to distribute their signals. In the past, a Low Noise Block converter (LNB) supply voltage (+13V/+18V) has been used to select between the two polarities of signals that were available on a single satellite network. Additionally, if signals from only two satellites are available for reception, then the presence or absence of a 22 kHz tone superimposed on the LNB supply voltage may be used to switch between either of the two satellite networks.
When the number of satellite networks grows beyond two, the voltage, and tone switching combination is no longer sufficient. One method to overcome this impediment is through bi-directional communications between an integrated receiver/decoder (IRD) and a satellite selector switch, such as used in the European standard known as DISEQ. The IRD sends a command signal to the selector switch to switch to a selected satellite network. The two-way (directional) protocol provides an avenue for feedback from the switch to the IRD. Thus, in an instance where the IRD sends a command to the selector switch, the selector switch upon switching, sends an acknowledgement message back to the IRD.
However, not all satellite systems utilize bi-directional protocols, rather many utilize unidirectional messaging. The problem encountered by an integrated receiver/decoder (IRD) using a unidirectional messaging system is that the IRD has no feedback from the switch. Thus, a message may be sent to the switch, nevertheless, the IRD has no way of knowing whether or not the switch actually received the message and then switched.
The lack of feedback may cause a problem if the user disconnects and reconnects the transmission coaxial cable, for example, in an attempt to reset the IRD and switch. The IRD will search for the lost satellite signal throughout each of the satellite networks by attempting to send messages to the switch, even though the switch is not connected to the IRD. When the user reconnects the switch via the coaxial cable, the switch will default to the prior transponder, which is not necessarily the transponder the IRD was expecting to switch to. Thus, the user will receive the wrong satellite signal.
Furthermore, the lack of feedback from the switch may cause a problem when the IRD sends a command signal that is degraded or incomplete (e.g., coaxial cable signal losses). In this instance, the switch may fail to properly select the correct transponder on a satellite or the correct satellite thereby sending the user an incorrect satellite signal.
Therefore, it is desirable to provide a method and apparatus for ensuring proper satellite network and transponder selection via the IRD and switch. It is also desirable to provide a form of feedback from the switch to indicate that the switch has failed to properly select a desired satellite signal.